Modelling the surface free energy parameters of polyurethane coats—part 2. Waterborne coats obtained from cationomer polyurethanes

Polyurethane cationomer coats were synthesised on the basis of typical diisocyanates, properly selected polyether polyols, HO-tertiary amines and HCOOH as quaternisation reagents. The values of their surface free energy (SFE) parameters were obtained by the van Oss-Good method, with the use of the contact angle values which had been found by the goniometric method. Based on the obtained findings, empirical models were developed which made it possible to anticipate the effects of the raw material types on the SFE values of the produced coats. The possibility was noted to adjust the SFE values within 25–50 mJ/m² by selecting carefully suitable parent substances. The principal consequences for the formation of improved hydrophobicity coats, applicable inter alia specialised protective coatings, were found to come not only from diisocyanate and polyol types but also from the alkylammonium cation structure which results from the use of different tertiary amines. The fundamental SFE lowering effect was noted when tertiary amines with 0–15 % of the 2,2,3,3-tetrafluoro-1,4-butanediol as a fluorinated chain extender was incorporated into polymer chains.     

Synthesis and characterisation of coating polyurethane cationomers containing quaternary ammonium alkyl groups derived from built-in alkyl bromides

Polyurethane cationomers were synthesised in the reaction of 4,4′-methylenebis(phenyl isocyanate) with polyoxypropylene glycol (M = 450) and N-methyl diethanolamine. Amine segments were built-in to the urethane–isocyanate prepolymer in the reaction with 1-bromoalkanes (C₂–C₁₀), and then they were converted to alkyl-ammonium cations. The obtained isocyanate prepolymers were then extended in the aqueous medium. That yielded stable aqueous dispersions which were applied on the surfaces of test poly(tetrafluoroethylene) plates. After evaporation of water, the dispersions formed thin polymer coatings. ¹H and ¹³C NMR spectral methods were employed to confirm chemical structures of synthesised cationomers. Based on ¹H NMR and IR spectra, the factors κ and α₁ or α₁ were calculated, which represented the polarity level of the obtained cationomers. The differential scanning calorimetry method revealed decline of T _g for the hard urethane and urea segments from 60 °C to 46 °C when the number of carbon atoms increased in the alkyl radical attached to the ammonium cation. Changes were discussed in the surface free energy (SFE) and its components, as calculated independently according to the methods suggested by van Oss-Good and by Owens–Wendt, in relation to chemical structures of cationomers. The growing length (from C₂ to C₁₀) of the alkyl radical attached to the N atom in the cationomer chain was found to reduce the value of SFE of the polymer coating from 46 to 28 mJ/m². That is caused by gradual weakening of long-range interactions, within which the highest share is taken by dispersion interactions.     

Chemical structure and surface properties of the polyurethane cationomers

Polyurethane cationomers were synthesised in the reaction of various diisocyanates with polyoxypropylene glycol and two N-alkyldiethanolamines. The obtained isocyanate prepolymers were then extended in the aqueous medium by means of 1,6-hexamethylenediamine; stable aqueous dispersions were thus obtained, which were applied to and distributed over the poly(tetrafluoroethylene) surface. After evaporation of water from those dispersions, thin polymer coatings were produced. The analyses with the use of ¹H, carbon-13 nuclear magnetic resonance and infrared spectroscopy methods confirmed chemical structures of synthesised cationomers. Also, attempts were made to quantitatively characterise polarities of those structures by means of factors that were defined especially for that purpose. Moreover, the physical model of van Oss–Good and wetting angles for coatings obtained from the polyurethane cationomers in question, measured with the use of standard liquids with various polarity specifications, were utilised to determine the surface free energy values for the obtained ionomers.     

Surface free energy of polyurethane coatings with improved hydrophobicity

The polarity of polyurethane coats was studied on the basis of the goniometric method for determination of wetting angle values, on the basis of calculated surface free energy (SFE) values by the van Oss-Good and Owens-Wendt methods, and on the basis of polarity measurements with the use of the (1)H NMR spectra. Test polyurethanes were synthesised in the reaction of methylene diphenyl 4,4'-diisocyanate (MDI) or 3-izocyanatomethyl -3,5,5- trimethylcyclohexyl isocyanate (IPDI) and polyoxyethylene glycols or polyesters poly(ε-caprolactone) diols and poly(ethyleneadipate) diol with different molecular weights, and some diols as chain extenders, in dioxane. The type of raw material was found to significantly affect the phase structure of the obtained polyurethane elastomers and to control physical interactions within those structures, thus influencing the SFE values. Fundamental reduction in the SFE value of a coating below 28?mJ/m(2) was achieved by the use of 2,2,3,3-tetrafluoro-1,4-butanediol as the urethane prepolymer chain extender.     

Synthesis and characterisation of coating polyurethane cationomers containing fluorine built-in hard urethane segments

Polyurethane cationomers were synthesised in the reaction of 4,4’-methylenebis(phenyl isocyanate) with polyoxyethylene glycol (M?= 2,000) or poly(tetrafluoroethyleneoxide-co-difluoromethylene oxide) α,ω-diisocyanate and N-methyl diethanolamine. Amine segments were built-in to the urethane-isocyanate prepolymer in the reaction with 1-bromobutane or formic acid, and then they were converted to alkylammonium cations. The obtained isocyanate prepolymers were then extended in the aqueous medium that yielded stable aqueous dispersions which were applied on the surfaces of test poly(tetrafluoroethylene) plates. After evaporation of water, the dispersions formed thin polymer coatings. ¹H, ¹³C NMR and IR spectral methods were employed to confirm chemical structures of synthesised cationomers. Based on ¹H NMR and IR spectra, the factors κ and α were calculated, which represented the polarity level of the obtained cationomers. The DSC, wide angle X-ray scattering and atom force microscopy methods were employed for the microstructural assessment of the obtained materials. Changes were discussed in the surface free energy and its components, as calculated independently according to the method suggested by van Oss–Good, in relation to chemical and physical structures of cationomers as well as morphology of coating surfaces obtained from those cationomers. Fluorine incorporated into cationomers (about 30%) contributed to lower surface free energy values, down to about 15 mJ/m². That was caused by gradual weakening of long-range interactions within which the highest share is taken by dispersion interactions.     

Polyurethane cationomers synthesised with 4,4′-methylenebis(phenyl isocyanate), polyoxyethylene glycol and <Emphasis Type="Italic">N</Emphasis>-methyl diethanolamine

Polyurethane cationomers with increased contents of ions were synthesised in the reaction of 4,4′-methylenebis(phenyl isocyanate) (MDI) with polyoxypropylene glycol (M = 450) and N-methyl diethanolamine (N-MDA). Amine segments were built-in to the urethane–isocyanate prepolymer in the reaction with formic acid and then they were converted to alkyl-ammonium cations. The obtained isocyanate prepolymers were then extended in the aqueous medium with the use of 1,6-hexamethylenediamine. That yielded stable aqueous dispersions, which were applied on the surfaces of test poly(tetrafluoroethylene) samples. After evaporation of water, the dispersions formed thin polymer coatings. ¹H and ¹³C NMR spectral methods were employed to confirm chemical structures of synthesised cationomers and to modify their quantitative composition in relation to that assumed on the basis of the stoichiometry of the reactions, which were conducted on successive stages of the polyaddition process. Furthermore, the GPC method was used to learn the sizes and distributions of mean molecular weights of those cationomers. Based on ¹H NMR spectra, the factor κ was calculated which represented the polarity level of the obtained cationomers. Good correlation was found between that factor and the free surface energy γ _S (increasing in the range 38–42 mJ/m²) as well as its polar and acid-base components, as determined from the van Oss–Good model on the basis of measured wetting angles between the coatings and model liquids with various polarities. The values of κ and γ _S parameters resulted principally from the increasing amounts of cations NH⁺, which were evaluated on the basis of the concentrations of tertiary nitrogen atoms increasing within 1.37–2.66 wt%. Those concentrations and amounts resulted, in turn, from the amounts of amine N-MDA which could be built into cationomers. The effects were discussed of chemical structures and polarity specifications of polyurethane cationomers on the viscosities of produced aqueous dispersions and on the sizes of their colloidal particles, on the values of free surface energy and on its polar and acid-base components, and on the glass transition temperatures T _g2 of the rigid segments as found by the differential scanning calorimetry (DSC) method.     

Modelling the surface free energy parameters of polyurethane coats—part 1. Solvent-based coats obtained from linear polyurethane elastomers

Polyurethane elastomers coating were synthesised by using typical diisocyanates, polyether and polyester polyols and HO-tertiary amines or diols as a chain extenders. Mole fractions of structural fragments (κ _exp) responsible for the polar interactions within polyurethane chains were calculated by ¹H NMR method. Obtained results were confronted with the analogous parameter values (κ _theor) calculated on the basis of process stoichiometry, considering the stage of the production of isocyanate prepolymers and reaction of their extension for polyurethanes. Trials of linear correlation between the κ _exp parameters and surface free energy (SFE) values of investigated coatings were presented. SFE values were determined by Owens–Wendt method, using contact angles measured with the goniometric method. Based on achieved results, another empirical models, allowing for prediction the influence of the kind of polyurethane raw materials on SFE values of received coatings were determined. It was found that it is possible to regulate the SFE in the range millijoules per cubic metre by the selection of appropriate substrates. It has been found that use of 2,2,3,3-tetrafluoro-1,4-butanediol as a fluorinated extender of prepolymer chains is essential to obtain coatings with increased hydrophobicity, applied among others as biomaterials—next to diphenylmethane diisocyanate and polyoxyethylene glycol.     

Study of ionomer blends based on a polyurethane cationomer and an acrylic anionomer

Polyurethane and polyurethane cationomers were synthesized using 2,3-dihydroxypyridine and 2,3-dihydroxypyridine hydrochloride as chain extenders. Poly(butyl methacrylate-co-methacrylic acid) was synthesized by free radical solution polymerization and was converted into its sodium salt. The polyurethane cationomer and the acrylic anionomer were blended in different proportions in N,N-dimethylformamide. Simple blends without ionic groups were also prepared. Miscibility enhancement in these systems was studied by means of differential scanning calorimetry and scanning electron microscopy.     

New glycosides from the Japanese fern Hymenophyllum barbatum

Thirteen glycosides and methyl (3R,5R)-5-hydroxy-(beta-D-glucopyranosyloxy)-hexanoate were newly isolated from the Japanese fern Hymenophyllum barbatum, although our previous work revealed the isolation of hemiterpene glycosides, hymenosides A-J, from the same species. The structures of the newly isolated glycosides were elucidated by extensive two-dimensional (2D) NMR and/or chemical evidence. The structures of those aglycones were divided into four types, 2-methyl-but-2-ene-1,4-diol, 2-hydroxymethyl-but-2-ene-1,4-diol, 2-methylene-butane-1,3,4-triol, and 3-hydroxy-5-hexanolide. The sugar moieties, which were acylated by phenylacetic acid derivatives, were also established by chemical and spectroscopic methods. Eight glucosides of the isolated compounds in the present investigation had a bitter or weakly pungent taste. It is clear that a phenylacetyl group attached to glucose or allose as an ester is necessary for the bitter taste.     

Aqueous dispersions of polyurethane cationomers: a new approach for hydrophobic modification and crosslinking

Polyurethanes (PUs) containing tertiary nitrogen atoms were synthesised from poly (tetramethylene oxide) glycol, toluene diisocyanate and N-methyl diethanolamine. These polymers were converted into cationomers by quarternising with alkyl bromides of different chain lengths and then dispersed in water. Finally the cationic PU dispersions were further crosslinked with dibromo compounds of different spacer lengths. The effect of percent ionisation, percent crosslinking, chain length of the ioniser and crosslinker on particle size, viscosity and interfacial tension of the dispersions and on the thermal, mechanical and surface tension properties of the dispersion cast films were studied. The hydrophilicity of the polymer is more in the dispersed state than when cast as a film, which exhibited low critical surface tension values. With increase in chain length of the ioniser and the crosslinker, the hydrophobicity of the dispersion cast film increases without appreciable change in the hydrophilicity of the polymer in the dispersed phase, as can be seen from the interfacial tension and critical surface tension values.     

New bitter-tasting hemiterpene glycosides from the Japanese fern Hymenophyllum barbatum.

Hymenosides G--J were newly isolated from the Japanese fern Hymenophyllum barbatum, in addition to hymenosides A--F. The structures of hymenosides were elucidated by extensive two-dimensional nuclear magnetic resonance and/or chemical evidence. The structures of those aglycones were divided into three types, 1,4-dihydroxy-2-hydroxymethyl-but-2-ene, 1,4-dihydroxy-2-methyl-but-2-ene, and 3-hydroxy-5-hexanolide. The sugar moieties were also established by chemical and spectroscopic methods, which were acylated by phenylacetic acid derivatives. These glycosides had a bitter or weakly pungent taste.     

Supercritical carbon dioxide extraction of volatiles from spices. Comparison with simultaneous distillation-extraction

Supercritical fluid extraction (SFE) and simultaneous distillation-extraction (SDE) were used to extract the essential oils from three different spices (oregano, basil, and mint), and a comparative study of extracts obtained using SFE and SDE is presented. Temperature and pressure for the SFE extraction were optimized prior to the experimental extractions. The extracts obtained using the two methods were very similar in composition, but SFE yielded better relative standard deviations and avoided the thermal degradation or solvent contamination of samples.     

Experimental and theoretical structural study of 2‐pyridyl‐ and 4‐hydroxyphenyl‐1,4‐dihydropyridine derivatives

A series of substituted 1,4‐dihydropyridines (1,4‐DHPs) has been synthesised following the well‐known Hantzsch's procedure for symmetrical 1,4‐DHP. The structures of these compounds have been thoroughly studied by X‐ray crystallographic analysis and semiempirical (AMI) calculations. A good agreement is found between the theoretical and experimental results. In all cases, the most stable conformation fulfils all the requirements needed for exhibiting an antagonist calcium effect.     

Wettability and surface composition of partly and fully regenerated cellulose thin films from trimethylsilyl cellulose

The wettability and surface free energy (SFE) of partly and fully regenerated cellulose model surfaces from spin coated trimethylsilyl cellulose were determined by static contact angle (SCA) measurements. In order to gain detailed insight into the desilylation reaction of the surfaces the results from SCA measurements were compared with data from other surface analytical methods, namely thickness measurements, X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance infrared spectroscopy (ATR-IR). Additionally, the influence of ultra high vacuum treatment (UHV) during XPS measurements on the water wettability and surface morphology of regenerated cellulose thin films was investigated. The wetting of polar and non-polar liquids increased with prolonged regeneration time, which is reflected in the higher SFE values and polarities of the films. After UHV treatment the water SCA of partly regenerated films decreases, whereas fully regenerated cellulose shows a higher water SCA. Therefore it is assumed that volatile desilylation products tend to adsorb on partly regenerated films, which strongly influences their wettability.     

Fat content for nutritional labeling by supercritical fluid extraction and an on-line lipase catalyzed reaction

A method using sequential supercritical fluid extraction (SFE) and enzymatic transesterification has been developed for the rapid determination of total nutritional fat content in meat samples. SFE conditions of 12.16 MPa and 50°C were utilized to extract lipid species from the sample matrix. The enzymatic transesterification of the lipids by methanol was catalyzed by an immobilized lipase isolated from Candida antarctica. Conversion of the triglycerides to fatty acid methyl esters was monitored by supercritical fluid chromatography, while the fatty acid content of the extract was determined by capillary gas chromatography (GC). Total fat, saturated fat and monounsaturated fat contents were calculated from the GC data and compared to values from traditional extraction and lipid determination methods. Both off-line SFE and automated SFE followed by on-line GC analysis using two different instruments were utilized in this study. The enzymatic-based SFE method gave comparable results to the organic solvent extraction-based method followed by conventional BF₃-catalyzed esterification.     

Translational isomerism and dynamics in multi-hydroquinone derived porphyrin [2]- and [3]-catenanes

A series of porphyrins strapped with polyether chains containing two or three 1,4-dioxybenzene units has been synthesised with a view to the production of porphyrin-containing [2] and [3]catenanes, where the porphyrin is strapped between ortho-positions of 5,15-(meso)-diaryl groups, and is interlinked with the bipyridinium macrocycle cyclobis(paraquat-4,4'-biphenylene). The porphyrins were isolated as mixtures of atropisomers, where the linking strap spans across the face of the porphyrin (alpha,alpha-isomer), or 'twisted' around its side (alpha,beta-isomer). Their structures were determined by detailed 1H NMR spectroscopy. The bis-1,4-dioxybenzene-strapped derivatives were shown to undergo atropisomerisation on heating, to produce an equilibrium mixture. Catenation under high pressure conditions of the mixture, or of the individual isomers, produced only a single catenane, that of the alpha,alpha-isomer. Its structure was determined by mass spectral and dynamic NMR measurements. Rates were determined for: (i) translational motion or 'shuttling' between 1,4-dioxybenzenes; (ii) 'rotation' of the macrocycle around the 1,4-dioxybenzene axis; and (iii) 'rocking' of the 1,4-dioxybenzene within the macrocycle. The atropisomers of the strapped derivatives containing three 1,4-dioxybenzene units were also separated, and subjected to catenation. Both [2]- and [3]catenanes were isolated, and were shown to be stable to further atropisomerisation. Their solution structures were probed in detail by dynamic 1H NMR measurements. The rates for shuttling and rotation were obtained in certain cases, although the complexity of the spectra of the [3]catenanes prevented a more detailed investigation.     

Polyurethane cationomers modified by polysiloxane

The synthesis of waterborne polyurethane cationomers was successfully carried out. Different proportions of α,ω‐di(hydroxyl)polydimethylsiloxane (PDMS) modifier (0–7.3% by weight) were applied. Analysis of IR spectra confirmed the structure of obtained polyurethane cationomers and the incorporation of a modifier into the polyurethane structure. The differential scanning calorimetry (DSC) method was employed for the microstructural assessment of the obtained materials. A clear decrease of the degradation temperature with increasing amounts of incorporated PDMS indicates immiscibility part of the polysiloxane segments with soft segments derived from polyethylene glycol. Changes were discussed in the free surface energy and its components, as calculated independently according to the method suggested by Owens–Wendt, in relation to chemical and physical structures of cationomers as well as morphology of coating surfaces obtained from those cationomers. Test results of contact angle measurements indicated that with increasing content of the polysiloxane in the analyzed films, the contact angles increase. Copyright © 2017 John Wiley & Sons, Ltd.     

Polyurethane cationomers. I. Structure–properties relationships

Polyurethane (PU) cationomers have been synthesized by quaternizing tertiary amine-containing linear polyurethanes using different quaternizers containing acid groups. The effect of chemical structure of PU cationomers on the physical properties was studied. The mechanical properties of PU cationomers were improved with decreasing molecular weight of poly(caprolactone) glycol, and increasing concentration of quaternary ammonium. Decreasing the carbon number in the alkyl group of the N-alkyl diethanol-amine chain-extenders, and using rigid symmetrical diisocyanates, the mechanical properties of the PU cationomers were increased. The effects of these factors on the glass transition temperature of PU cationomers were also examined. The mechanical properties of the PU cationomers decreased by immersion in water and recovered after removal of the water.     

Hyperbranched polycyclocarbosiloxane

A new cross-linkable naphthalene-cyclocarbosiloxane was synthesised starting from bis[1,4-bis(methylhydrosiloxanyl)-dihydronaphthalene] via catalytic addition of the Si-H reactive groups to the unsaturated bond of triethoxyvinylsilane. Hyperbranched polycyclocarbosiloxane networks were formed by condensation of the alcoxyl groups in the presence of dibutyltin dilaurate as catalyst. The cross-linking process was studied in order to obtain information concerning the values of the reaction parameters and to determine the position of the gelation point relative to conversion.GPC analysis, IR, and 1H-NMR spectral analysis techniques were used to investigate the chemical structures of the intermediates and of the product.     

Supercritical fluid extraction of halogenated monoterpenes from the red alga Plocamium cartilagineum

Supercritical fluid extraction (SFE) of the marine red alga Plocamium cartilagineum, which is known to contain complex mixtures of halogenated monoterpenes, was investigated. P. cartilagineum samples were extracted by SFE with carbon dioxide and modified carbon dioxide containing up to 10% methanol at different pressure and temperature conditions to establish the optimum conditions for extraction. These conditions were then used in the extraction of halogenated monoterpenes from 2 different samples of P. cartilagineum: one from Davenport, CA, and the other from Casa Beach (San Diego, CA). Several halogenated monoterpenes isolated by conventional solvent extraction with methanol and purified by column chromatography were used as the reference compounds for the determination of the extraction efficiency in the SFE experients. Plocamium cartilagineum belongs to the red alga family--Plocamiaceae, and has been found to contain a large number of halogenated monoterpenes, whose structures typically contain 1-6 bromine and/or chlorine atoms. P. cartilagineum grows along the Pacific coast from Washington to Chile, the British Isles, Australia, and Spain. Interestingly, P. cartilagineum collected from different geographical areas in the world are all reported to produce halogenated monoterpenes, but of different structural types and halogen substitution patterns. Most of these halogenated monoterpenes have been found to exhibit varied biological activities, including antifungal, antimicrobial, and molluscicidal activity.